1. Field of the Invention
The present invention relates to a system for dynamically providing adjustable support for work pieces and, more specifically, to an adjustable system for providing support for printed circuit boards or other substrates typically having components mounted on one side during installation of other components on the other side.
2. The Prior Art
There are many operations within the manufacturing environment that require work-pieces to be well supported while operations are being performed on it. This is especially true where the work-piece itself is made from flexible materials or where the work-piece is flexible due to its design such as where it is thin or its length or width make it flexible. Other work-pieces may have an irregular surface such as the surface of a printed circuit board (PCB) that has components installed on one side and require additional operations to be performed on its opposite side during its assembly.
Within electronic assembly operations, and especially within the surface mount electronic manufacturing industry, most operations performed on PCB substrates require proper support that keeps the work-piece flat and level. Among them are printing, glue dispensing, epoxy encapsulation, pick-and-place, inspection and reflow.
There are two operations within electronic assembly where substrate support currently has had its strongest demand. They are “printing”, whereby a substrate has a stencil or screen brought near the PCB substrate, the stencil or screen having apertures corresponding to the land pattern on the PCB, and whereby solder paste is then wiped across the stencil or screen with a squeegee that deposits paste onto the PCB substrate's individual lands, so that when the stencil or screen is lifted away, the paste remains on the PCB substrate's lands; and “pick-and-place” operations that are essentially robotic placement of components onto the PCB substrate, those components having pin-outs that are placed onto the appropriate lands of the PCB substrate.
These operations have had strong demand for underside support because pressure is applied to the top surface of the substrate as operations are performed to its top-side. Other operations may need support simply to keep substrates flat and level.
PCB substrate support has a long history, especially with the inception of surface mount technologies. Initially, printing of solder paste was done by individual deposition onto substrate lands, but the industry quickly adopted techniques from the silkscreen printing industry. Here, one could apply paste through a stencil onto the lands with a single pass of a squeegee. Because the squeegee had to be applied with a fair amount of pressure, the substrate had to be supported underneath to prevent the PCB from flexing.
When components were placed onto the substrate, the PCB might bounce, and even though the pressures were lower than squeegee pressures by an order of magnitude, they too required support during this operation.
To facilitate underside substrate support virtually all printing and pick-and-place operations adopted the use of a lifting table with support articles strategically placed onto the table that would then lift up and meet the substrate prior to the operations commencing. This technique is still in use today, having become even more critical when electronic assemblies started placing components on both sides of the PCB substrate.